1. Field of the Invention
The present invention provides a metallurgical lance for injecting solid particulate material into a vessel.
One application of the lance is as a means for injecting metallurgical feed material into the molten bath of a vessel in a process (such as a direct smelting process) for producing molten metal.
2. Description of Related Art
A known direct smelting process, which relies on a molten metal layer as a reaction medium, and is generally referred to as the HIsmelt process, is described in International application PCT/AU96/00197 (WO 96/31627) in the name of the applicant.
The HIsmelt process as described in the International application is a molten bath-based direct smelting process which has particular application for producing molten ferrous metal from ferrous feed material (such as ores, partly reduced ores, and metal containing waste streams). The HIsmelt process includes:
(a) forming a bath of molten iron and slag in a vessel;
(b) injecting into the bath:
(i) a metalliferous feed material, typically metal oxides; and
(ii) a solid carbonaceous material, typically coal, which acts as a reductant of the metal oxides and a source of energy; and
(c) smelting metalliferous feed material to metal in the metal layer.
The term xe2x80x9csmeltingxe2x80x9d is herein understood to mean thermal processing wherein chemical reactions that reduce metal oxides take place to produce liquid metal.
The HIsmelt process also includes post-combusting reaction gases, such as CO and H2, released from the bath in the space above the bath with oxygen-containing gas and transferring the heat generated by the post-combustion to the bath to contribute to the thermal energy required to smelt the metalliferous feed materials.
The HIsmelt process also includes forming a transition zone above the nominal quiescent surface of the bath in which there is a favourable mass of ascending and thereafter descending droplets or splashes or streams of molten metal and/or slag which provide an effective medium to transfer to the bath the thermal energy generated by post-combusting reaction gases above the bath.
In the HIsmelt process the metalliferous feed material and solid carbonaceous material is injected into the metal layer through a number of lances/tuyeres which are inclined to the vertical so as to extend downwardly and inwardly through the side wall of the smelting vessel and into the lower region of the vessel so as to deliver the solids material into the metal layer in the bottom of the vessel. In a commercially operating process the lances must withstand hostile conditions, including operating temperatures of the order of 1400xc2x0 C., within the smelting vessel for prolonged periods, typically at least several months. The lances must accordingly have an internal forced cooling system to operate successfully in this harsh environment and must be capable of withstanding substantial local temperature variations. The present invention enables the construction of lances that are able to operate effectively under these conditions.
According to the invention, there is provided an elongate metallurgical lance to extend into a vessel for injecting solid particulate material into molten material held within the vessel, which lance includes:
(a) a central core tube through which to pass the solid particulate material;
(b) an annular cooling jacket surrounding the central core tube throughout a substantial part of its length, which jacket defines an inner elongate annular coolant flow passage disposed about the core tube, an outer elongate annular coolant flow passage disposed about the inner coolant flow passage, and an annular end flow passage interconnecting the inner and outer annular coolant flow passages at a forward end of the jacket;
(c) coolant inlet means for inlet of coolant into the inner annular coolant flow passage of the jacket at a rear end region of the jacket; and
(d) coolant outlet means for outlet of coolant from the outer annular coolant flow passage at the rear end region of the jacket, whereby to provide for flow of coolant forwardly along the inner annular coolant flow passage to the forward end of the jacket then through the annular end flow passage and backwardly through the outer annular coolant flow passage,
and wherein:
(i) an outer wall of a forward end section of the jacket is formed from a first material which has high heat transfer properties and can withstand external temperatures above 1100xc2x0 C. for prolonged periods when the jacket is cooled by coolant flow;
(ii) an outer wall of a body section of the jacket is formed from a second material that maintains its structural properties when exposed to external temperatures above 1100xc2x0 C. for prolonged periods when the jacket is cooled by coolant flow, whereby the outer wall acts as a structural member that contributes to supporting the lance at these temperatures; and
(iii) the outer wall of the forward end section and the outer wall of the body section are welded together.
The above-described combination of high heat transfer and structural sections of the lance makes it possible to make the lance relatively long so that;
(a) the entry position of the lance into a vessel that contains a molten bath of metal and slag can be in a side wall of the vessel above the quiescent slag layer, and necessarily above the very hostile hearth region of the vessel; and
(b) the lance extends downwardly and inwardly a sufficient distance to deliver feed material into a central portion of the hearth region.
Locating the entry point of the lance in this position, ie above the quiescent slag layer, also makes it possible for the lance to be changed-over if necessary while the vessel still holds molten metal and slag. Thus, lance change-over does not necessitate a major shut-down of the vessel involving draining the vessel.
Preferably the jacket includes a transition section positioned between the outer wall of the forward end section and the outer wall of the body section and the transition section is welded to both outer walls.
Preferably the wall thickness of the outer wall of the body section is less than that of the outer wall of the forward end section.
Preferably the wall thickness at one end of the transition section is substantially the same as that of the outer wall of the forward end section and the wall thickness at the other end of the transition section is substantially the same as that of the body section.
Preferably the temperatures are above 1200xc2x0 C.
More preferably the temperatures are above 1300xc2x0 C.
Preferably the first material is copper or a copper alloy.
Preferably the second material is steel.
Preferably the transition section is formed from steel.
Preferably the weld between the forward end section and the transition section is buttered with nickel or a nickel alloy.
Preferably the outer wall of the jacket includes keying formations for solidification of slag onto the outer wall.
Preferably the keying formations have an undercut or dove-tail cross-section.
Preferably the length of the lance that, in use, is self-supporting, is at least 1.5 meters.
Preferably the inner and outer annular coolant flow passages and the annular end flow passage of the jacket are defined by:
(a) an inner tube and an outer tube interconnected at a forward end of the jacket by an annular bullnose end connector to form a single hollow annular structure which is closed at the forward end of the jacket by the annular bullnose end connector; and
(b) an elongate tubular structure disposed within the hollow annular structure and having (i) a tube part which extends within it to divide the interior of the hollow annular structure into said inner and outer elongate annular flow passages and (ii) a forward end part disposed adjacent the annular bullnose end connector of said hollow annular structure such that the annular end flow passage is defined between said forward end part of the tubular structure and the annular bullnose end connector of said hollow annular structure.
Preferably the outer tube includes a forward part and a rearward part welded together.
More preferably the forward part of the outer tube defines the outer wall of the forward end section of the jacket that is formed from the first material.
More preferably also the rearward part of the outer tube defines the outer wall of the body section of the jacket that is formed from the second material.
More preferably the outer tube includes the transition section positioned between and welded to the forward and rearward parts.
More preferably the bullnose end connector is formed from the first material.
Preferably the forward end part and the tube part of the elongate tubular structure are welded together.
Preferably the bullnose end connector is welded to each of the inner tube and the outer tube.
Preferably the weld connections between the following components of the jacket are axially spaced to facilitate assembly of the jacket:
(i) the bullnose end connector and the inner tube;
(ii) the bullnose end connector and the outer tube; and
(iii) the forward end part and the tube part.
Preferably the core tube includes a nozzle that has one part that is located partially within and is shielded by the cooling jacket and another part that extends beyond the cooling jacket, and the nozzle has a threaded rear end that engages a complementary threaded section of the core tube so that the nozzle can be readily attached and detached from the core tube.
Preferably the annular end flow passage curves smoothly outwardly and backwardly from the inner annular coolant flow passage to the outer annular coolant flow passage and the effective cross-sectional area for water flow through the annular end flow passage is less than the cross-sectional flow areas of both the inner and outer annular coolant flow passages.
Preferably further the single hollow annular structure is mounted so as to permit relative longitudinal movement between the inner and outer tubes thereof due to differential thermal expansion or contraction thereof and the elongate tubular structure is mounted to accommodate that movement.
Preferably the coolant is water.
According to the present invention there is also provided a vessel for operating a molten bath-based process for smelting ferrous feed material to produce molten ferrous metal which includes a hearth, a side wall extending upwardly from the hearth, and at least one of the above-described metallurgical lance extending through the side wall and into the vessel.
Preferably the dimensions of the lance are selected such that the lance extends at least 1.5 meters into the vessel and is self-supporting over that length.
Preferably the self-supporting length of the lance is at least 2.5 meters.
Preferably the lance extends downwardly through the side wall of the vessel into a hearth region of the vessel at an angle of 30 to 60xc2x0 to the horizontal.
Preferably the side wall includes a section formed from water-cooled panels and the lance extends through that section.